Principle of High-Efficiency Diodes

In modern electronic devices and power systems, high-efficiency diodes play an indispensable role. From mobile phone chargers and the electronic control systems of new energy vehicles to the energy conversion devices of solar power generation, high-efficiency diodes are relied upon to achieve efficient power transmission and conversion. To deeply understand the principle of high-efficiency diodes, we need to start from the basic working mechanism of diodes and then explore the key factors enabling their high efficiency step by step.

Basic Working Principle of Diodes

A diode is a semiconductor device with unidirectional conductivity. Its core structure is formed by the combination of P-type semiconductor and N-type semiconductor, and the junction between them is called the PN junction. In the P-type semiconductor, the concentration of holes (which can be regarded as positively charged carriers) is relatively high; in the N-type semiconductor, the concentration of electrons (negatively charged carriers) is relatively high. When the PN junction is formed, due to the carrier concentration difference, electrons in the N region diffuse into the P region, and holes in the P region diffuse into the N region. As a result, a space charge region, also known as the depletion layer, is formed near the PN junction. An internal built-in electric field exists in the depletion layer, pointing from the N region to the P region. This electric field hinders the further diffusion of carriers. When the diffusion and drift movements reach a dynamic equilibrium, the state of the PN junction stabilizes.

When a forward voltage is applied to the diode, that is, the P region is connected to the positive pole of the power supply and the N region is connected to the negative pole, the external electric field is opposite to the built-in electric field, and the depletion layer becomes narrower, which is conducive to the diffusion of carriers. At this time, holes in the P region and electrons in the N region can smoothly pass through the PN junction, forming a forward current, and the diode conducts. When a reverse voltage is applied, that is, the P region is connected to the negative pole of the power supply and the N region is connected to the positive pole, the external electric field is in the same direction as the built-in electric field, the depletion layer becomes wider, and the diffusion of carriers is difficult. Only a small number of minority carriers (electrons in the P region and holes in the N region) generated by thermal excitation form a weak reverse current under the action of the electric field, and the diode is in the off state